In the simplest terms, thermocouples are essentially a type of thermometer; more specifically, they act as temperature sensors, using electromagnetics, as opposed to physical changes, to determine temperature. Thermocouples are used in a wide range of applications, from cement and oil and gas to power generation and pulp and paper.Get more news about K Type PEEK THERMOCOUPLE wire,you can vist our website!

These versatile measuring devices are comprised of two wire legs, made of different materials, welded together at the temperature-sensing end, or temperature measurement junction — where temperature is measured. When this junction — the hot junction — registers a different temperature than the reference or “cold” junction, located at the other end of the thermocouple, voltage is created; this reaction is known as the thermoelectric effect. An electron flowmeter at the cold junction detects the voltage and converts it into a temperature reading.
Resistance temperature detectors (RTDs) are similar to thermocouples in that they use electric properties to detect temperature, but they operate in a fundamentally different manner. While thermocouples rely on the thermoelectric effect of voltage creation, RTDs measure temperature by resistance and do not require specialized wire. Though similar, thermocouples and RTDs are not interchangeable.

Thermocouple Wire Types
Depending on the specific application, a wide range of wire materials can be used in thermocouples. Determining a thermocouple’s chemical resistance, vibration resistance, general durability, temperature range, and so on, different materials allow thermocouples to withstand different environmental conditions — thereby dictating the applications that a given thermocouple can be used in.
According to ANSI/ASTM standards, thermocouples are designated type ratings based on the materials of the wire, such as chromel, alumel, or constantan. The most popular thermocouple wire types are as follows:

Nickel Alloy Thermocouple Types
Type K — Comprised of a chromel (an alloy of roughly 90% nickel and 10% chromium, available in several different grades) positive conductor and an alumel (a 95% nickel, 2% aluminum, 2% manganese, 1% silicon alloy) negative conductor, type K thermocouples are among the most affordable and can be found in a wide variety of applications, with operating temperatures ranging from -454 °F to 2300 °F.
Type J — Type J thermocouples feature an iron positive conductor and a negative conductor made of constantan (a copper alloy of 55% copper and 45% nickel). These thermocouples have a slightly smaller temperature range as well as a shorter lifespan, and are not ideal for high-temperature oxidizing environments. Type J is usually found in older equipment that is incompatible with other thermocouple wire types.
Type T — Constructed of a copper positive conductor and constantan negative conductor, type T thermocouples also have a smaller temperature range. Commonly employed in electrical generators, these thermocouples provide superior stability.
Type E — Featuring a chromel positive conductor and constantan negative conductor, type E thermocouples are ideal for extremely low-temperature applications, such as cryogenics and freezers.